You know when you have limited information about someone but you feel like you can still form a full opinion on them? Like, maybe you see their twitter feed and they misspell every other word but think they are smart? And they act like know-it-alls but they really know nothing? So you read what they write and you totally get who this person is. You know she is a completely uneducated, trashy, judgmental moron who sees herself as above everyone else - even though she has a shitty job and no car and lives in a white-trash town and her ex-man is even trashier than she is.
So you have a pretty fully-formed opinion of this person, despite not knowing this person and not wanting to. Maybe you think to yourself, perhaps if we met I would feel differently, when I just have to hear her talk and not read her ignorance? Maybe she aren't so bad in real life.
And then, this person comes out as a Donald Trump supporter and it reinforces the fact that your judging skills are 100% on point and that everything you inferred about this person is 100% fact.